Application of a deep convolutional neural network in the images colorization problem

Object of the research are modern structures and architectures of neural networks for image processing. Goal of the work is improving the existing image processing algorithms based on the extraction and compression of features using neural networks using the colorization of black and white images as an example. The subject of the work is the algorithms of neural network image processing using heterogeneous convolutional networks in the colorization problem. The analysis of image processing algorithms with the help of neural networks is carried out, the structure of the neural network processing system for image colorization is developed, colorization algorithms are developed and implemented. To analyze the proposed algorithms, a computational experiment was conducted and conclusions were drawn about the advantages and disadvantages of each of the algorithms.This work was supported by the Russian Foundation for Basic Research, research No 17-08-01569

Origin and Properties of the Gap in the Half-Ferromagnetic Heusler Alloys

We study the origin of the gap and the role of chemical composition in the half-ferromagnetic Heusler alloys using the full-potential screened KKR method. In the paramagnetic phase the C1_b compounds, like NiMnSb, present a gap. Systems with 18 valence electrons, Z_t, per unit cell, like CoTiSb, are semiconductors, but when Z_t > 18 antibonding states are also populated, thus the paramagnetic phase becomes unstable and the half-ferromagnetic one is stabilized. The minority occupied bands accommodate a total of nine electrons and the total magnetic moment per unit cell in mu_B is just the difference between Z_t and $2 \times 9$. While the substitution of the transition metal atoms may preserve the half-ferromagnetic character, substituting the $sp$ atom results in a practically rigid shift of the bands and the loss of half-metallicity. Finally we show that expanding or contracting the lattice parameter by 2% preserves the minority-spin gap.Comment: 11 pages, 7 figures New figures, revised tex

Mild C-H functionalization of alkanes catalyzed by bioinspired copper(ii) cores

Three new copper(ii) coordination compounds formulated as [Cu(H1.5bdea)2](hba)·2H2O (1), [Cu2(μ-Hbdea)2(aca)2]·4H2O (2), and [Cu2(μ-Hbdea)2(μ-bdca)]n (3) were generated by aqueous medium self-assembly synthesis from Cu(NO3)2, N-butyldiethanolamine (H2bdea) as a main N,O-chelating building block and different carboxylic acids [4-hydroxybenzoic (Hhba), 9-anthracenecarboxylic (Haca), or 4,4′-biphenyldicarboxylic (H2bdca) acid] as supporting carboxylate ligands. The structures of products range from discrete mono- (1) or dicopper(ii) (2) cores to a 1D coordination polymer (3), and widen a family of copper(ii) coordination compounds derived from H2bdea. The obtained compounds were applied as bioinspired homogeneous catalysts for the mild C-H functionalization of saturated hydrocarbons (cyclic and linear C5-C8 alkanes). Two model catalytic reactions were explored, namely the oxidation of hydrocarbons with H2O2 to a mixture of alcohols and ketones, and the carboxylation of alkanes with CO/S2O82- to carboxylic acids. Both processes proceed under mild conditions with a high efficiency and the effects of different parameters (e.g., reaction time and presence of acid promoter, amount of catalyst and solvent composition, substrate scope and selectivity features) were studied and discussed in detail. In particular, an interesting promoting effect of water was unveiled in the oxidation of cyclohexane that is especially remarkable in the reaction catalyzed by 3, thus allowing a potential use of diluted, in situ generated solutions of hydrogen peroxide. Moreover, the obtained values of product yields (up to 41% based on alkane substrate) are very high when dealing with the C-H functionalization of saturated hydrocarbons and the mild conditions of these catalytic reactions (50-60 °C, H2O/CH3CN medium). This study thus contributes to an important field of alkane functionalization and provides a notable example of new Cu-based catalytic systems that can be easily generated by self-assembly from simple and low-cost chemicals. This journal is © The Royal Society of Chemistry

Coordination Polymers Driven by Carboxy Functionalized Picolinate Linkers: Hydrothermal Assembly, Structural Multiplicity, and Catalytic Features

This work explores an N,O-donor dicarboxylic acid, 5-(3-carboxyphenyl)picolinic acid (H2cpic), as an adjustable linker for generating diverse types of coordination polymers (CPs). Eight new compounds were hydrothermally assembled, completely characterized, and formulated as [Mn(μ3-cpic)(H2O)2]n (1), [Cd2(μ3-cpic)(μ4-cpic)(H2O)2]n (2), [Cd(μ4-cpic)]n (3), [Mn(μ-cpic)(phen)(H2O)]n (4), [Zn(μ-cpic)(phen)]n·nH2O (5), [Cd2(μ-cpic)2(phen)2(H2O)]·3H2O (6), [Cd(μ3-cpic)(phen)]n (7), and [Zn2(μ-cpic)2(bipy)(H2O)2]n·4nH2O (8). Products 1-8 were assembled from H2O solutions containing the respective metal(II) chloride salts, H2cpic, NaOH, and an N-donor crystallization mediator (optional: 1,10-phenanthroline, phen; or 2,2′-bipyridine, bipy). The structural types of 1-8 include a dimer complex (6), one-dimensional (1, 4, 5, 7, 8) and two-dimensional (2) CPs, and a three-dimensional (3) metal-organic framework. Hydrothermal reaction temperature, type of metal(II) center, and presence of mediators of crystallization are the factors responsible for structural diversity of 1-8. Thermal behavior, topological features, and catalytic properties of these products were studied. Notably, CP 1 acts as an effective, stable, and recyclable catalyst for the heterogeneous cyanosilylation of different aldehydes under mild conditions, resulting in quantitative conversion of aldehyde substrates to respective cyanohydrin products (99% product yields). Compounds 1-8 expand the usage of H2cpic for the assembly of functional coordination polymers, thus stimulating further research in this swiftly growing field. © 2021 American Chemical Society

Interplay between H-bonding and interpenetration in an aqueous copper(ii)-aminoalcohol-pyromellitic acid system: self-assembly synthesis, structural features and catalysis

Two new copper(ii) coordination compounds, [Cu(H1.5mdea)2]2(H2pma) (1a) and [{Cu2(μ-Hmdea)2}2(μ4-pma)]n·2nH2O (1b), were self-assembled at different temperatures from the same multicomponent reaction system, comprising copper(ii) nitrate, N-methyldiethanolamine (H2mdea), pyromellitic acid (H4pma), and potassium hydroxide. Products 1a and 1b were isolated as microcrystalline solids and fully characterized and their structures were established by single-crystal X-ray diffraction. Compound 1a features the bis-aminoalcohol(ate) monocopper(ii) units and H2pma2− anions that are multiply interconnected by strong H-bonds into a firm 2D H-bonded layer. Compound 1b reveals the bis-aminoalcoholate dicopper(ii) motifs that are interlinked by the μ4-pma4− spacers into a 3D + 3D interpenetrated metal-organic framework. From a topological perspective, both networks of 1a and 1b are uninodal and driven by similar 4-connected H2pma2− or pma4− nodes, but result in distinct sql and dia topologies, respectively. Compound 1a was applied as an efficient catalyst for two model cycloalkane functionalization reactions: (1) oxidation by H2O2 to form cyclic alcohols and ketones and (2) hydrocarboxylation by CO/H2O and S2O8 2− to form cycloalkanecarboxylic acids. The substrate scope, effects of various reaction parameters, selectivity and mechanistic features were also investigated. © The Royal Society of Chemistry

Aminoalcoholate-driven tetracopper(II) cores as dual acetyl and butyrylcholinesterase inhibitors: Experimental and theoretical elucidation of mechanism of action

Three coordination compounds featuring different types of tetracopper(II) cores, namely [O ⊂ Cu4{N(CH2CH2O)3}4(BOH)4][BF4]2 (1), [Cu4(μ4-H2edte)(μ5-H2edte)(sal)2]n·7nH2O, (H4edte = N,N,N′,N′-tetrakis(2-hydroxyethyl)ethylenediamine, H2sal = salicylic acid) (2), and [{Cu4(μ3-Hbes)4(μ-hba)}K(H2O)3]n, H3bes = N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid (3), were assayed for their potency to inhibit the acetyl (AChE) and butyrylcholinesterase (BuChE) enzymes aiming to test these compounds as potential dual inhibitors in the treatment of Alzheimer's disease. All the investigated compounds showed a strong inhibitory potency toward both enzymes with IC50 values in micromolar range of concentration; compound 1 displayed the most potent inhibitory behaviour toward both enzymes. The mechanism of the AChE and BuChE inhibition was examined by enzyme kinetic measurements. The obtained kinetic parameters, Vmax and Km indicated an uncompetitive type of inhibition of both enzymes by compound 1. For the other two compounds a non-competitive inhibition mode was observed. To get further insight into the mechanism of action and to elucidate binding modes in details we examined the interactions of 1–3 with acetylcholinesterase, using molecular docking approach. Grid based docking studies indicated that these compounds can bind to peripheral anionic site (PAS) of the AChE with Ki values in micromolar range. Moreover, blind docking revealed the capability of investigated compounds to bind to new allosteric site (i.e. binding site II) distinct from PAS. Showing that these Cu-based compounds can act as new allosteric inhibitors of AChE and identifying novel allosteric binding site on AChE represents a significant contribution toward the design of novel and more effective inhibitors of AChE. © 2020 Elsevier Inc

H-Bonded and metal(ii)-organic architectures assembled from an unexplored aromatic tricarboxylic acid: structural variety and functional properties

This study reports the application of an aromatic tricarboxylic acid, 2,5-di(4-carboxylphenyl)nicotinic acid (H3dcna) as a versatile and unexplored organic building block for assembling a new series of metal(ii) (M = Co, Ni, Zn, Fe, and Mn) complexes and coordination polymers, namely [M(Hdcna)(phen)2(H2O)]·H2O (M = Co (1), Ni (2)), [Zn(µ-Hdcna)(phen)]n(3), [Co(µ-Hdcna)(bipy)(H2O)2]n·nH2O (4), [Zn2(µ-Hdcna)2(bipy)2(H2O)4]·6H2O (5), [Zn(µ3-Hdcna)(H2biim)]n(6), [Ni2(Hdcna)2(µ-bpb)(bpb)2(H2O)4] (7), [Fe(µ4-Hdcna)(µ-H2O)]n·nH2O (8), and [Mn3(µ5-dcna)2(bipy)2(H2O)2]n·2nH2O (9). Such a diversity of products was hydrothermally prepared from the corresponding metal(ii) salts, H3dcna as a principal multifunctional ligand, and N-donor mediators of crystallization (1,10-phenanthroline, phen; 2,2'-bipyridine, bipy; 2,2'-biimidazole, H2biim; or 1,4-bis(pyrid-4-yl)benzene, bpb). The obtained products1-9were fully characterized by standard methods (elemental analysis, FTIR, TGA, PXRD) and the structures were established by single-crystal X-ray diffraction. These vary from the discrete monomers (1,2) and dimers (5,7) to the 1D (3,4,6) and 2D (8,9) coordination polymers (CPs). Structural and topological characteristics of hydrogen-bonded or metal-organic architectures in1-9were highlighted, revealing that their structural multiplicity depends on the type of metal(ii) source and crystallization mediator. Thermal stability as well as luminescent, magnetic, or catalytic properties were explored for selected compounds. In particular, the zinc(ii) derivatives3,5, and6were applied as efficient heterogeneous catalysts for the cyanosilylation of aldehydes with trimethylsilyl cyanide at room temperature. The catalytic reactions were optimized by tuning the different reaction parameters (solvent composition, time, catalyst loading) and the substrate scope was also explored. Compound5revealed superior catalytic activity leading to up to 75% product yields, while maintaining its original performance upon recycling for at least four reaction cycles. Finally, the obtained herein products represent the unique examples of coordination compounds derived from H3dcna, thus opening up the use of this multifunctional tricarboxylic acid for generating complexes and coordination polymers with interesting structures and functional properties. © The Royal Society of Chemistry 2020

Synthesis, structural features, and catalytic activity of an iron(Ii) 3d coordination polymer driven by an ether-bridged pyridine-dicarboxylate

New iron(II) three-dimensional coordination polymer (3D CP), [Fe(µ3-Hcpna)2 ]n (1), was assembled under hydrothermal conditions from 5-(4’-carboxyphenoxy)nicotinic acid (H2 cpna) as a trifunctional organic N,O-building block. This stable microcrystalline CP was characterized by standard methods for coordination compounds in the solid state (infrared spectroscopy, elemental analysis, thermogravimetric analysis, powder and single-crystal X-ray diffraction). Structure and topology of 1 were examined and permitted an identification of a 3,6-connected framework of the rtl topological type. In addition, compound 1 acts as effective catalyst precursor for oxidative functionalization of alkanes (propane and cyclic C5 −C8 alkanes) under homogeneous catalysis conditions, namely for the oxidation of saturated hydrocarbons with H2 O2/H+ system to produce ketones and alcohols, and for alkane carboxylation with CO/H2 O/S2 O8 2− system to obtain carboxylic acids. The influence of an acid promoter and substrate scope (propane and cyclic C5 −C8 alkanes) were investigated. © 2019 by the authors. Licensee MDPI, Basel, Switzerland

Introducing a flexible tetracarboxylic acid linker into functional coordination polymers: synthesis, structural traits, and photocatalytic dye degradation

This work describes the application of an unexplored aromatic tetracarboxylate building block, 2,3′,4,4′-diphenyl ether tetracarboxylic acid (H4deta), for the synthesis of manganese(ii) and cadmium(ii) coordination polymers (CPs). Five new products, formulated as [Mn2(μ6-deta)(phen)2]n(1), [Cd2(μ6-deta)(phen)2]n(2), [Mn2(μ6-deta)(2,2′-bipy)2]n(3), [Cd2(μ5-deta)(4,4′-bipy)2(H2O)2]n·2nH2O (4), and [Cd2(μ6-deta)(py)(H2O)2]n(5), were assembled using a hydrothermal protocol from the respective metal(ii) chlorides, H4deta, and different mediators of crystallization, namely 1,10-phenanthroline (phen), 2,2′-bipyridine (2,2′-bipy), 4,4′-bipyridine (4,4′-bipy), or pyridine (py). All the CPs1-5were obtained as stable crystalline products and characterized by conventional solid-state methods (elemental analysis, FTIR, UV-vis, TGA, and PXRD) and single-crystal X-ray diffraction. The structures of1-3feature decorated honeycomb-like 2D double layers of a 3,6L66 topological type. Compound4reveals a trinodal 4,4,5-connected 3D metal-organic framework (MOF) with a unique topology, while the 2D coordination polymer5discloses a binodal 4,6-connected layer with a 4,6L45 topology. The structural and topological traits, thermal stability, luminescence properties and photocatalytic activity toward methylene blue degradation were studied for the obtained compounds. In particular, MOF4acts as an active, stable, and recyclable photocatalyst for the UV-light-assisted discoloration of methylene blue in water under ambient conditions. By introducing a novel type of flexible tetracarboxylic acid linker, the present study discloses the first manganese and cadmium compounds derived from H4deta as an unexplored polycarboxylate building block, thus contributing to intensive research on functional metal-organic architectures. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2020

Coordination Polymers from 2-Chloroterephthalate Linkers: Synthesis, Structural Diversity, and Catalytic CO2Fixation

In contrast to the broad use of terephthalic acid as a building block for generating metal-organic architectures, functionalized terephthalate ligands remain significantly less investigated. In the present study, 2-chloroterephthalic acid (CltaH2) was used as an unexplored linker for assembling a new series of metal(II) coordination polymers (CPs) formulated as {[Cu2(μ-Clta)(μ4-Clta)(bipy)2]·2H2O}n (1), {[Cu2(μ-Clta)(μ4-Clta)(phen)2]·2H2O}n (2), [Co3(μ4-Clta)3(phen)2]n (3), {[Zn4(μ3-Clta)2(μ4-Clta)(μ3-OH)2(phen)2]·2H2O}n (4), {[Cd(μ3-Clta)(phen)]·H2O}n (5), [Co2(μ-Clta)(μ4-Clta)(μ-bpa)2]n (6), [Zn2(μ4-Clta)(μ4-biim)]n (7), and [Cd(μ-Clta)(H2biim)2]n (8). These compounds were prepared hydrothermally from the respective metal(II) chlorides, CltaH2, and different N-donor supporting ligands acting as mediators of crystallization (i.e., bipy, 2,2′-bipyridine; phen, 1,10-phenanthroline; bpa, bis(4-pyridyl)amine; H2biim, 2,2′-biimidazole). The structures of the coordination polymers 1-8 range from one-dimensional chains (5 and 8) and two-dimensional layers (1-3) to three-dimensional (3D) frameworks (4, 6, and 7); the latter also include 3D + 3D interpenetrated examples (4, 6). Apart from different dimensionalities, the compounds also feature distinct topologies, namely, 3,4L13 in 1 and 2, 3,4,6L12 in 3, pcu in 4, SP 1-periodic net (4,4)(0,2) in 5, sqc65 in 6, 2C1 in 8, and a new kir1 topology in 7. Given the similarity of the reaction conditions, the obtained wide diversity of structures is primarily determined by the type of metal(II) node and/or crystallization mediator. All the CPs were also screened as heterogeneous catalysts in a model CO2 fixation reaction, namely, in the coupling of epoxide (epichlorohydrin) with carbon dioxide, under atmospheric pressure, and in the absence of added solvent, to produce the corresponding cyclic carbonate. The catalytic reactions were optimized for CP 4, which revealed the best activity (up to 71% product yields), good stability, and recyclability for up to four reaction steps. Finally, CPs 3-8 are the first examples of cobalt, zinc, and cadmium coordination compounds assembled from 2-chloroterephthalic acid, thus widening its very limited application in the design of functional metal-organic architectures.